NEWS |


Work to accelerate on India’s first regional rapid transit system


Robbins XRE TBM breaks through in the Andes CHILE - Having bored through challenging variable ground with rock strengths of up to 60MPa UCS, a Robbins Crossover XRE TBM has broken through in the mountainous southern Maule region of Chile. Working under 450m maximum


overburden, the 4.6m-diameter machine excavated a 3.3km-long tunnel for the Los Condores Hydroelectric Power Project, owned by power company Enel Chile. The machine faced varying conditions including tuff, sandstone, breccia and conglomerate with sections of high-pressure water inflows. Crossover TBMs are suited to Andean


sedimentary and volcanic-type geology, where rock strengths and hydrogeological conditions vary greatly. Maximum advance rates reached 605.8m in one month and 212.8m in one week. The Crossover machine featured a heavy


Above: The TBMs passed factory acceptance tests at Terratec’s facility and were then transported to India to undergo site assembly


INDIA - Following the delivery of three Terratec EPB tunnel boring machines, tunnelling works are now gearing up on India’s first regional rapid transit project which will connect Delhi and Meerut, via the city of Ghaziabad. Contractor Afcons Infrastructure


will use the new 7.51m-diameter TBMs for Package 8 ‘Brahampuri down-ramp to Begumpul up- ramp’ section of the Delhi-Meerut Regional Rapid Transit System Project (Delhi-Meerut RRTS). The package comprises a 7.12km tunnel and three underground stations. Having passed their factory


acceptance tests at Terratec’s facility and been transported to India, the TBMs will then be reassembled on site and launched in early 2022. Starting from Bhaisali station, the machines will bore different alignments through sand, silt and clay, passing beneath dense urban areas. One of the TBMs will then navigate an extreme right radius towards Begampul station. To tackle the expected geology, Terratec has included dome-type


8 | February 2022


cutterheads which, for added versatility, have been designed to allow cutting tools to be exchanged for 17in (432mm) disc cutters; this will allow the TBMs to bore through diaphragm walls and cope with unexpected obstacles, such as old wells or foundations. As the TBMs progress, they


will install 300mm x 1,500mm reinforced concrete universal-style, precast lining rings comprising six segments plus key. Muck removal, segment transport and logistics supply will be via rolling stock using five 45t battery locomotives (also supplied by Terratec). In contrast to a typical metro


system, the Delhi-Meerut RRTS will cater for those looking to travel longer distances at higher speeds and with fewer stops. Currently under construction, the 82.15km-long, semi-high-speed rail corridor is anticipated to be operational by 2025 and will see maximum speeds of 180km/h, allowing the distance between Delhi and Meerut to be covered in less than 60 minutes.


duty, centrally-mounted screw conveyor for the duration of the drive. The TBM remained in hard-rock configuration with muck chute installed, along with paddles, bucket lips, scrapers and disc cutters. Around 75% of the excavation was performed using the main drive gearboxes in high torque configuration – EPB or low-speed mode. The cutterhead and screw conveyor were never changed to EPB mode. A key challenge to the project was high-


pressure groundwater inflows. During ring installation, water was prevented from draining through the rear shield drilling ports and the screw conveyor rear gate was closed. Inflows of up to 5,500Lit (1,500gal)/minute were encountered, making back-fill grout injection behind the concrete segments a challenge. Instead of grout injection through the tail shield ports, grout was injected directly through the concrete segments with hoses. This was more flexible and reduced the need for re-injections.


Tunnel sector mourns the passing of Axel Nitschke US - Tunnelling professionals globally are mourning the premature death of US-based Dr Axel Nitschke, who died peacefully on December 26. He was 54 and a much valued contributor to T&T. He had a distinguished tunnelling career in both the US and Germany. By the time his career tragically ended, he had worked with some of the biggest names in tunnel consultancy, leading tunnelling projects in the US, Canada, South America and Europe.


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